Applied Anatomy Of Subtemporal Transmandibular Approach For Lateral Skull Base Exposure

Part oneThe microanatomy research of subtemporal transmandibular approach to expose lateral skull base by imitating operation Objective In order to understand the microsurgical anatomy of the subtemporal transmandibular approach to expose the lateral skull base and obtain the detailed anatomical parameters for clinical operation, and more important, to improve the operative effects of the communicative tumors in lateral and middle skull base,we designed and performed the anatomical study.Methods Ten adult cadaveric specimens (20 sides) were observed and measured by imitating operations through the subtemporal transmandibular approach. Under operative microscope, dissections were performed to emphasize the relationships between bone, muscles, and neurovascular structures in the surgical region. All data were statistically processed and presented in the mean±sd (range of measured values) style. Results The frontotemporal branch of the facial nerve ran between the superficial temporalis fascia and the superficial layer of the deep temporalis fascia or in the superficial temporalis fascia. Infratemporal fossa and pterygopalatine fossa exhibited complicated microanatomical structures. The lateral pterygoid muscle took up most of the infratemporal fossa. The maxillary artery was the largest terminal branch of the external carotid artery and divided into three segments: mandibular segment, pterygoid segment, pterygopalatine segment. Mandibular segment located 20.4±1.7mm (16.8-23.4) below the joint capsule. Pterygoid and pterygopalatine segment showed obvious anatomic variations.Thepterygoid plexus had superficial and deep components and the second was the most prominent one in our study. The mandibular nerve divided into an anterolateral (mainly motor) trunk and a posteromedial (mainly sensory) trunk. Parapharyngeal space divided into prestyloid and retrostyloid compartments by styloid process and fascias. There were internal carotid artery, jugular vein and the IX,X,XI,XII cranial nerves in the retrostyloid space.Conclusion The subtemporal transmandibular approach is useful for resection of the tumors occupying infratemporal fossa, parapharyngeal space, pterygopalatine fossa, and the middle skull base, especially for huge communicative tumors. This approach has good exposure and the microanatomy related to it is complex. Systemic knowledge of the anatomy are mandatory for mastering this complicated approach. Part two Anatomy of bone structures related to subtemporal transmandibularapproachObjective To study the anatomy of the bone structures related to the subtemporal transmandibular approach and provide an advisable anatomy reference for exposure.Methods Observing and measuring of the bone structures exposed in imitating operations on 10 cadaveric adult specimens (20sides) by subtemporal transmandibular approach. After operation, the soft tissues adherent to the specimens were removed and the other osseous structures concerned to this approach were studied.All data were statistically processed and presented in the mean±sd (range of measured values) style. Results Zygomatic arch was an anatomical key for medial skull base and infratemporal fossa exposure. The length of it and the width of the mandibular fossa were (32.9±2.6)mm and (15.5±1.3)mm respectively.